The London Zoo silverback gorilla that escaped in early October drank five litres of blackcurrant juice before he was recaptured by zookeepers.
An in-house investigation into the incident said Kumbuka made an 'opportunistic' exit through two unlocked doors into an area where zookeepers were working.
Kumbuka then threw back five litres of undiluted blackcurrant squash while briefly exploring the area next to his den, before being tranquilised and moved to safety.
Armed police were called to the central London zoo and visitors were evacuated following the gorilla's escape on October 13.
Professor David Field, the zoo's zoological director, said the escape was undramatic, and that Kombuka was kept calm because of a staff member who had a close bond with Kumbuka.